1. Field of the Invention
This invention relates to aqueous detergent concentrates adapted to be diluted by the consumer prior to use.
2. Description of Related Art
There is a trend in the household products and personal care industries to provide products in concentrated form which are adapted to be diluted with water by the consumer prior to use. This approach reduces the bulk of packaging which needs to be disposed of by the consumer and reduces the shipping and handling costs associated with distribution of such products.
Aqueous liquid concentrates such as laundry, fine fabric and dishwasher detergents are normally provided with a high content of active ingredients such that, when diluted by the consumer per packaging instructions, the diluted product will contain an amount of active ingredients normally present in a non-concentrated product.
However, the provision of concentrated liquids gives rise to a number of problems, including viscosity control and stability.
Concentrated liquids tend to exhibit a higher viscosity due to the high content of surfactants, builders, electrolytes and other components present in the concentrate. Concentrates having viscosities in excess of 10,000 cps (mPas) tend to be difficult to pour from the packaging container, while pourable concentrates tend to have insufficient viscosity on the other hand when appropriately diluted by the consumer, thereby reducing consumer appeal. Also, surfactants present at high levels in such concentrates tend to form closely spaced, suspended lamellar structures which tend to contact one another after periods of storage, resulting in a flocculation phenomenon which destabilizes the suspension and leads to a marked increase in product viscosity.
One approach to dealing with poor post-dilution viscosity is to include in the liquid concentrate formulation one or more organic or inorganic thickening agents such as swelling clays, alumina, gums, polymeric materials or cellulosic polymers. However, the use of such thickening additives tends to worsen the problem of concentrate pourability and imparts only a minimal viscosity increase to the diluted concentrate.
Hydrophilic polymeric materials have also been used in liquid detergent concentrates as viscosity control agents. For example, U.S. Pat. No. 4,715,969 discloses that the addition of less than about 0.5% by weight of a polyacrylate polymer, e.g., sodium polyacrylate, having a molecular weight from about 1,000 to 5,000, to aqueous detergent compositions containing primarily anionic surfactants will stabilize the viscosity of the composition and prevent a major increase in viscosity after a period of storage of the formulated composition. Also, EPO 301,883 discloses similar compositions containing from about 0.1 to 20% by weight of a viscosity reducing, water soluble polymer such as polyethylene glycol, dextran or a dextran sulfonate.
While these and other approaches tend to enhance concentrate pourability, they do not solve the problem of poor post-dilution viscosity.
Accordingly, it is an object of the invention to provide a liquid detergent concentrate which exhibits a sufficiently low viscosity such that it is pourable as a free flowing liquid from its packaging container and which also exhibits a viscosity after appropriate dilution with water which is preferably at least equal to the viscosity of the original, undiluted concentrate.